OutOfPlaneBend force fix

plugins/amoeba/platforms/cuda/src/kernels/kCalculateAmoebaCudaLocalForces.cu

@@ -1163,16 +1163,26 @@ void kCalculateAmoebaLocalForces_kernel()
             float bkk3              = (rdb2 != 0.0f ) ? bkk2/rdb2    : 0.0f;
                   bkk2              = rdb2 - bkk2;
 
+            float adXcd_0           = yad*zcd - zad*ycd;
+            float adXcd_1           = zad*xcd - xad*zcd;
+            float adXcd_2           = xad*ycd - yad*xcd;
+            float adXcd_nrm2        = adXcd_0*adXcd_0 + adXcd_1*adXcd_1 + adXcd_2*adXcd_2;
+
+            float adXcd_dot_db      = xdb*adXcd_0 + ydb*adXcd_1 + zdb*adXcd_2;
+                  adXcd_dot_db     /= sqrt(rdb2*adXcd_nrm2);
+
             float angle;
+/*
             if( bkk3 < 1.0e-6f ){
                 angle             = sqrtf( bkk3 );
             } else if( bkk3 < 0.98f ){
                 float cosine      = sqrtf(1.0f - bkk3);
                 angle             = acos(cosine);
             } else {
-                float sin         = sqrtf(bkk3);
-                angle             = asin(sin);
+                angle             = abs( asin(adXcd_dot_db) );
             }
+*/
+                angle             = abs( asin(adXcd_dot_db) );
                 
             // find the out-of-plane energy and master chain rule terms